We have performed a systematic study of the Bremsstrahlung emission from the electrons in the plasma of a commercial 14.5 GHz Electron-Cyclotron Resonance Ion Source. The electronic spectral temperature and the product of ionic and electronic densities of the plasma are measured by analyzing the Bremsstrahlung spectra recorded for several rare gases (Ar, Kr, Xe) as a function of the injected power. Within our uncertainty, we find an average temperature of ≈ 48 keV above 100W, with a weak dependency on the injected power and gas composition. Charge state distributions of extracted ion beams have been determined as well, providing a way to disentangle the ionic density from the electronic density. Moreover X-ray emission from highly charged argon ions in the plasma has been observed with a high-resolution mosaic crystal spectrometer, demonstrating the feasibility for high-precision measurements of transition energies of highly charged ions, in particular of the magnetic dipole (M1) transition of He-like of argon ions.

For many years there has been a need to find an alternative to the radioisotope-based gamma-gamma density (GGD) measurement. The traditional GGD measurement uses the scattering of 662-keV gamma rays from a 137 Cs radioisotopic source to determine formation density. A statistically precise measurement requires a 40-GBq or higher source strength and such a logging source, with a 30.17-year half-life, may pose health, security, and environmental risks.Pulsed-neutron generators have been used in the industry for several decades in wireline tools and more recently in logging-while-drilling tools. These generators produce 14-MeV neutrons, many of which interact with the nuclei in the formation through inelastic collisions. These inelastic interactions are typically followed by the emission of a variety of highenergy gamma rays. Similar to the case of the GGD measurement, the transport and attenuation of these gamma rays is a strong function of the formation density. However, the gamma-ray source is now distributed over a volume within the formation, where gamma rays have been induced by neutron interactions and the source can no longer be considered to be a point as in the case of a radioisotopic source. In addition, the extent of the induced source region depends on the transport of the fast neutrons from the source to the point of gamma-ray production.Even though the physics is more complex, it is possible to measure the formation density if the fast neutron transport is taken into account when deriving the density answer. This paper reviews the physics underlying the sourceless neutron-gamma density (SNGD) measurement, explains the various facets of the algorithm used for its computation and details the different environmental effects that may influence the measurement.The successful application of the method is shown in several log examples.

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